A drive mechanism used in a conventional radio-controlled model tank (RC tank) will be explained below. The RC tank has a receiver provided on the vehicle body thereof to receive control signals from a transmitter of a radio control unit. A control part provided on the vehicle body controls left and right motors mounted on the vehicle body on the basis of the received control signals so that the motors are rotated forward or backward and so forth. The left and right motors transmit power to left and right140 caterpillars of the RC tank independently of each other.
FIG. 4 illustrates an RC tank arranged as stated above. A radio control unit 100 has a left lever 101 for outputting control signals for a left motor 105 and a right lever 102 for outputting control signals for a right motor 106. If the left and right levers 101 and 102 are simultaneously actuated forward or backward by the same amount, a control part 104 provided on a vehicle body 103 outputs signals to the left motor 105 and the right motor 106 to rotate them at the same speed. The signals are amplified in amplifiers 105a and 105b to drive the respective motors 105 and 106, thereby causing the RC tank to travel forward or backward. During the forward or backward traveling, if the amount of actuation of one lever is reduced, the rotational speed of the caterpillar rotated by one motor reduces, and the vehicle body turns. The control part 104 on the vehicle body 103 outputs signals to the left motor 105 and the right motor 106 to rotate them at the same speed, and the signals are amplified in the left and right amplifiers 105a and 105b to drive the respective motors.
Meanwhile, as shown in FIG. 5, a radio control unit 200 of a radio-controlled car (RC car) or the like has two control levers, of which a left lever 201 is actuated to perform speed control, and a right lever 202 is used for steering control. This type is common in RC cars. A control part 204 on a vehicle body 203 outputs signals to a motor 205 and a steering servo 206. The signal output to the motor 205 is amplified in an amplifier 205a to drive the motor 205.
Under these circumstances, attempts to make the operation of the remote controller for RC tanks similar to that for RC cars have been proposed, for example, in Patent Document 1 and Patent Document 2 that was presented by this applicant. The RC tanks in these patent documents have left and right motors that are independent of each other in the same way as in the above-described RC tank. The radio control units of these RC tanks, however, have a left lever for throttling and a right lever for steering. A control part processes actuating signals of the left and right levers in a software manner to change the rotational speeds and rotational directions of the left and right motors, thereby controlling turning and forward and backward traveling of the RC tank.    Patent Document 1: Japanese Patent Application Publication No. Hei 11-221370    Patent Document 2: Japanese Patent Application Publication No. 2002-306860